If the computer was off, it seems to me that it's more of a sign that it was either shut off improperly (by turning it off with the switch or a power failure) or there's a corrupt file somewhere in the loading sequence. Corrupt files can be caused by many things.
A top-notch computer expert in Omaha says it sounds as if it were caused by a "poor installation" of Windows XP, when that was put in.
He suggests I forget all about it, mostly because distance is a factor, the main factor, involved here, and just to get another used tower and hard-drive. He knows my attitude; it's a crap game when one gets used stuff, in which sometimes one wins, sometimes one loses, and one accepts both wins and losses without getting all agog and excited about them.
It's a learning experience, and fortunately not a too-expensive learning experience; I guess what I learned from this was that when one gets a used computer, get it with one of those "start-up" (or "operating systems") discs.
Of course for years I had been aware of the need for a "start up" disc, but on the other hand, I never had to use one, and so never bothered.
I am assuming a "start up" disc and "operating systems" disc are the same thing.